Item 27 - Water Supply Assessment for Cabrillo Town Center Project

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Santa Ana 2020 Urban Water Management Plan arcadis.com 6-21 MWDOC’s imported water sales to OCWD since FY 1990-91 averages approximately 31,200 AF per year. Recently, due to low Santa Ana River flows as a result of low precipitation and increased use along the river, OCWD has needed to purchase more imported replenishment water per year than the average of 31,200 AFY over the last 25 years (this does not include water amounts from MET’s Conjunctive Use Program (CUP) or its Cyclic Storage Account). However, with the emergence of PFAS affecting groundwater production, the need to purchase imported water has been temporary suspended. Until PFAS treatment is in place for most groundwater producers in the region, imported replenishment water will be significantly reduced. 6.3.7 MET Conjunctive Use Program / Cyclic Storage Program with OCWD Since 2004, OCWD, MWDOC, and certain groundwater producers have participated in MET’s CUP. This program allows for the storage of MET water in the OC Basin. The existing MET program provides storage up to 66,000 AF of water in the OC Basin to be pumped by participating producers in place of receiving imported supplies during water shortage events in exchange for MET’s contribution to improvements in basin management facilities and an annual administrative fee. These improvements include eight new groundwater production wells, improvements to the seawater intrusion barrier, and construction of the Diemer Bypass Pipeline. The water is accounted for via the CUP program administered by the wholesale agencies and is controlled by MET such that it can be withdrawn over a three-year time period (OCWD, 2020). As of 2021, the CUP has not been in use since 2014. The CUP contract ends in 2028. The Cyclic Storage account is an alternative storage account with MET. However, unlike the CUP program, OCWD controls when the water is used. The Cyclic Water Storage Program allows MET to store water in a local groundwater basin during surplus conditions, where MET has limited space in its regional storage locations. Once the water is stored via direct delivery or In-lieu the groundwater agency has the ability to purchase this water at a future date or over a 5-year period. 6.3.8 Overdraft Conditions Annual groundwater basin overdraft, as defined in OCWD's Act, is the quantity by which production of groundwater supplies exceeds natural replenishment of groundwater supplies during a water year. This difference between extraction and replenishment can be estimated by determining the change in volume of groundwater in storage that would have occurred had supplemental water not been used for any groundwater recharge purpose, including seawater intrusion protection, advanced water reclamation, and the in-Lieu Program. The annual analysis of basin storage change and accumulated overdraft for water year 2019-20 has been completed. Based on the three-layer methodology, an accumulated overdraft of 200,000 AF was calculated for the water year ending June 30, 2020. The accumulated overdraft for the water year ending June 30, 2019 was 236,000 AF, which was also calculated using the three-layer storage method. Therefore, an annual increase of 36,000 AF in stored groundwater was calculated as the difference between the June 2019 and June 2020 accumulated overdrafts (OCWD, 2021).